The present invention relates to communication control apparatus, especially, used in computer networks.
Computer networks in which computers are connected by communication lines to make mutual exchange of information possible are increasing steadily.
In this computer network, computers are connected via communication control devices to communication lines in order to determine a procedure to perform communication and to accurately control timing for transmission and receiving.
The communication control device is controlled by a communication control program. There are various versions of a communication control program depending upon the performance of the function improvement or debugging.
On the other hand, communication control programs are individually updated for the respective communication control devices constituting the computer network.
Thus when transmission from one station to another is to be performed, there exists a situation where communication may be impossible because of different versions of a program. Especially, when a new station is added to the computer network, a version of a communication control program for the communication control device of the newly added station is not consistent with those for other stations, resulting in the possibility that connection will be difficult.
In order to improve such a situation, a method has been developed in which a function such that communication between different versions of a communication program is enabled is provided by the communication control program itself. There is, however, the problem with this method that the process for executing the communication control program becomes complicated.
Another method is that both the communication control programs for the communication control devices which are intended to communicate therebetween are updated simultaneously. According to this method, however, simultaneous updating of both the programs is required, so that the entire computer network must be stopped at that time, giving rise to the problem that communication efficiency is lowered.